The movement of putative amino acid neurotransmitters between cells and extracellular fluid is under study. Several experimental approaches are in use: perfusion of the spinal subarachnoid space in the rat; measurement of endogenous amino acid release from tissue slices; assessment changes in cerebrospinal fluid amino acid concentration which accompany changes in brain amino acid concentration; and study of the changes in cerebral arterio-venous concentration differences for amino acids during seizures. Specific studies will include: attempts to induce the release of gamma-aminobutyric acid from the spinal cord into the spinal fluid by the use of uptake inhibition, analogue exchange, and receptor blockade; determination of amino acid flux in vitro after administration of neuroleptic drugs in vivo; and measurement of the cisternal fluid and cerebral venous taurine concentration during electrically-induced seizures in the rat. BIBLIOGRAPHIC REFERENCES: Cutler, R.W.P., Release of amino acids from the spinal cord in vitro and in vivo. Adv. Exp. Med. & Biol., 69: 435-446, 1976. Korobkin, R., and Cutler, R.W.P., Maturational changes of amino acid concentration in cerebrospinal fluid of the rat. Neurology, 26: 386, 1976.